How to increase the height in a lively way?

Question

I’m on a project and I need an object on the side of the page that increases the height as the scroll.

The result I have achieved so far is "breaking" as I go down the scroll. How to get something that is more lively or has a smoother transition?

HTML:

<header>
</header>
<div id="content">
    <div id="broca">
    </div>
</div>
<footer>    
</footer>

CSS:

header, footer{
    display:block;
    height:200px;
    background:red;
    width:100%;
}
#content{
    display:block;
    width:100%;
    height:1500px;
    background:blue;
}
#broca{
    width:50px;
    height:0;
    background:#000;
}

jQuery:

$(function(){
    $(window).scroll(function() {
        var $broca = $('#broca');
        var st = $(this).scrollTop();
        if (st > $broca.height()){
            $broca.height( st );
        }
        if( st == 0 ) {

        } else {
            $broca.show();
        }
    }).scroll();
})

Jsfiddle

Answer 1

You can use the .animate, but as scroll does run multiple animates at the same time, it can still present some stops, the solution I found was to use the .clearQueue looks like it’s gotten more linear:

$(function(){
    $(window).scroll(function() {
        var $broca = $('#broca');
        var st = $(this).scrollTop();
        if (st > $broca.height()){
            $broca.clearQueue().animate({
                height: st } , 1000);
        }
        if( st == 0 ) {

        } else {
            $broca.show();
        }
    }).scroll();
})

(just adjust the speed as desired, maybe make a calculation as the size of st)

Jsfiddle

Answer 2

I noticed that in your example when climbing the scroll bar the size of the div does not follow as it happens when going down the scrollbar, so I rang, I do not know if this is what I wanted, but I figured, if you do not want to let me know in the comments.

I applied the property animate() that creates change css with a transition;

So any questions let me know I’ll do my best to help you.

Jsfiddle